Method of inhibiting cuprene formation in ethynylation reaction

Abstract

When acetylene flow to the continuous, aqueous ethynylation reaction of formaldehyde and acetylene, using a copper acetylide complex as the catalyst, is interrupted, resulting cuprene formation can be inhibited by maintaining the reaction mass at a pH of 3.5-5 until normal acetylene flow is resumed.

I claim: 
     
       1. In the continuous aqueous reaction of formaldehyde and acetylene to form 1,4-butynediol, run at a pH of 6-8 and using a copper acetylide complex as the catalyst, a method of inhibiting cuprene formation when the acetylene flow to the reaction mass is interrupted, the method comprising maintaining the reaction mass at a pH of about 3.5-5 until the normal flow of acetylene is resumed. 
     
     
       2. The method of claim 1 in which the pH is brought into the range 3.5-5 by adding to the reaction mass a monocarboxylic acid which has an ionization constant of about 1×10 -3  to 1×10 -5 , is miscible with water in all proportions and does not complex with the catalyst or form a compound which interferes with the reaction. 
     
     
       3. The method of claim 2 in which the acid is formic acid. 
     
     
       4. The method of claim 1 in which the catalyst is modified with bismuth and the pH is maintained in the range of 4.5-5. 
     
     
       5. In the continuous aqueous reaction of formaldehyde and acetylene to form 1,4-butynediol, using a copper acetylide complex as the catlyst and the addition of a basic material to control pH in the range of 6-8, a method of inhibiting cuprene formation when the acetylene flow to the reaction mass is interrupted which comprises maintaining the formaldehyde-acetylene reaction mass at a pH of 3.5-5 by adjusting the rate of addition of basic material, until normal acetylene flow is resumed.